THE BLOG

Despite years of arguing new housing will exacerbate traffic congestion and blaming the county’s urbanists for indifference to the problem of congestion, Marin Against Density (MAD) is now fighting against new traffic lanes on Sir Francis Drake (Drake), arguing the project will actually reduce capacity. Fact check: it won’t.

The project

Drake Boulevard is a mess south of Ross from every perspective. To people on foot or bike, it’s a hot, loud, dangerous traffic sewer. To people in cars, it’s a congested nightmare every rush hour. Thankfully, there’s enough space on the road to make the first problem a little less bad and fix the second problem.*

The biggest change to Drake would be a third lane heading south from Marin Catholic to 101 and, in one design, north from 101 to El Portal by narrowing lanes from between 15 and 21 feet to a standard 11 feet. This will increase capacity by about 50 percent along the most congestion stretches of the road, a huge boost for drivers that have complained about for years.

Other changes would be squaring off intersections in a few sections to make it safer to walk, new shoulders – formerly Class II bike lanes – and wider sidewalks [2]. Given that there are schools along the route, these are victories for parents and children along the way.

So what’s the problem?

According to an email from MAD [3], and to comments from anti-urbanists from the last time I tackled this problem in November [4], the primary complaint is that narrowing lanes will reduce capacity by slowing traffic. They’ve labelled it a traffic calming exercise, designed to support safety rather than traffic flow.

Even if we look past the morally reprehensible attitude that the safety of people walking isn’t worth protecting, it’s utterly illogical. MAD doesn’t understand how roads work.

A short primer on road capacity functions is in the notes, if you’re interested, but here’s the short of it: moving from a 12-foot lane to an 11-foot lane will decrease the free-flow speed of a road by about 3 percent, but adding a whole new lane will increase capacity much more than what’s lost by that very slight depression in free-flow speed. Add it all up, and the project should boost capacity by 45.5 percent.

But what about right-turn lanes lost? There is still more road capacity, so while the far right lanes might be slower during off-peak times, through drivers who won’t be in the far right lanes won’t need to worry.

To put it very simply, the county wants to slow uncongested travelers by about 3 percent to add 50 percent capacity. This seems like the kind of project MAD would support if it was so worried about traffic.

But MAD’s opposition to adding makes so little sense it boggles the mind. Why would an organization that argued any new homes will cause congestion fight against measures that might actually reduce congestion? The political answer might be the easiest.

It’s an election season, and that Fairfax email was rife with disparaging words for incumbent supervisor Katie Rice and glowing words for the conservative, Kevin Haroff, who has come out against the project [5]. By painting this redesign as a road diet rather than the road widening it is, MAD and its fellow organizations (CVP and Citizen Marin) can say that Rice has no solutions and is beholden to the madness of us urbanists.

If it’s about politics, then MAD is lying about the project to help their candidate and Haroff is complicit in the deception.

Of course, lots of anti-urbanists see a conspiracy to destroy Marin’s character. They probably actually believe that adding bike lanes is just part of that conspiracy. Al Dugan thinks I work for an anti-Marin lobbying group in DC, for instance.

So some people are playing the political game and don’t care if they’re on the technically correct side of a given issue or not as long as their candidate wins. Others want their candidate to win because they think only by cleaning house can they halt the spread of dangerous ideas in Marin. It’s a potent mix, and it‘s leading Marin down a dark path.

If even a project that will boost traffic capacity by nearly 50 percent is successfully painted as a congestion-causing project, there’s something seriously wrong with our politics. When we can’t even agree on what’s real or not, we cannot have a successful government. Fairfax went through this during Frank Egger’s years on the council. San Anselmo is going through its own turmoil with Ford Greene. Sausalito and Marinwood are going through phases when the whole governing body is dominated by people who take this sort of confrontational and personal approach to governing.

The Drake project has its problems, and I’ve highlighted them before, but as a symbol of our political dysfunction it is extremely worrying.

Notes

* For today, I’m not going to get into induced demand and the Fundamental Law of Traffic Congestion, which Connor Jones went over this past winter [6]. That’s a deeper problem, but fixing it is something nobody has the political stomach to take on even in San Francisco, let alone Marin.

** Traffic capacity – how many vehicles a road can carry in an hour – is a function of a road’s design speed and the road’s traffic jam density, or how many vehicles fit per mile when traffic speeds are basically zero:

This is called the Greenshields model, which is a reasonable tool for analyzing roads like this. Among other things, it tells us that as speed decreases, the number of cars the road can move per hour actually increases, at least up to a point. This is thanks to the fact that the space between cars decreases as speed decreases, allowing the road to be used more efficiently. Generally speaking, this is around Level of Service (LOS) grade E, though engineers try to keep LOS at around C or D to ensure some slack in the system [7].

According to this model, reducing the free-flow speed by 3 percent in this model to add a new lane will increase the maximum capacity by roughly 45.5 percent.